Page 278 - CITS - ED - Mechanical

ENGINEERING DRAWING - CITS

can be used to create 2D or 3D computer models. A CAD drawing is a file that consists of numeric data in binary
form that will be saved onto a disk.
Why should you use CAD?

Traditional drafting is repetitious and can be inaccurate. It may be faster to create a simple "rough" sketch by hand
but larger more complex drawings with repetitive operations are drawn more efficiently using CAD.
Why use AutoCAD?
AutoCAD is a computer aided design software developed by Autodesk Inc. AutoCAD was first introduced in 1982.
By the year 2000,it is estimated that there were over 4 million AutoCAD users worldwide.
What this means to you is that many employers are in need of AutoCAD operators. In addition, learning AutoCAD
will give you the basics for learning other CAD packages because many commands, terms and concepts are used
universally.
Learning to use a CAD system is similar to learning a new language. It is necessary to begin with the basic alphabet
and learn how to use it correctly and effectively through practice. This will require learning some new concepts and
skills as well as learning a different vocabulary. Today, the majority of the Mechanical CAD systems are capable
of creating three-dimensional solid models. Nonetheless, all CAD systems create designs using basic geometric
entities and many of the constructions used in technical designs are based upon two-dimensional planar geometry.
The method and number of operations that are required to accomplish the basic planar constructions are different
from one system to another.

In general, a Computer Aided Design (CAD) package has three components: a) Design, b) Analysis, and c)
Visualization, as shown in the sketch. A brief description of these components are follows as Fig 1.

Fig 1

Hardware and Software overview: There are two parts of a computer system, hardware and software, and a
CADD system in no exception. Computer hardware is the physical components of the computer such as system
unit, monitor and plotter. Computer software is the program that determines the application of a system.
There are three main categories of computers with respect to hardware:
• Mainframe.

• Minicomputer.
• Microcomputers, for example personal computers ( PCs).
CADD software: A CADD program contains hundreds of functions that enable you to accomplish specific drawing
tasks. A task may involve drawing an object, editing and existing drawing, displaying a view of the drawing, printing
or saving it, or controlling any other operation of the computer. The functions contain a number of commands that
enable you to specify exactly what you want to do and how you want to do it.
The functions are organized into modules that provide easy access to all the commands. The program is divided
into modules such as draw, edit, data output, function control, data storage and management. A program may also
have a number of specialized functions such as layers, database and 3D. Let s have a look at the CADD modules.
• Draw.
• Edit.
• Data output.
• System control.
• Data storage and management.

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CITS : Engineering Drawing (Mechanical) - Exercise 12